An Indonesian woman rides the back of a motorcycle BAY ISMOYO-AFP-Getty ImagesA city in Indonesia's Islamic law stronghold of Aceh will ban women from straddling male drivers on motorbikes, its mayor said on Wednesday, dubbing the position "improper".

The move comes after leaders from the country's only province ruled by strict sharia law drafted a series of new bills including banning women from wearing tight trousers, stoning adulterers and flogging homosexuals.

Under the new law, women in Lhokseumawe city, on the northern tip of Sumatra island, will have to sit "side-saddle" with their legs dangling off to one side.

"Women sitting on motorbikes must not sit astride because it will provoke the male driver. It's also to protect women from an undesirable condition," mayor Suaidi Yahya told AFP.

"It's improper for women to sit astride. We implement Islamic law here."

Women are allowed to straddle motorbikes if they are driving, as long as they are dressed "in a Muslim way", Yahya said.

The mayor plans to publicise the ban in coming weeks and will discuss sanctions with local Muslim clerics before issuing a formal regulation.